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       helptext - GRASS GIS Quickstart

       GRASS GIS Quickstart GRASS GIS Quickstart

Geographic Resources Analysis Support System

       GRASS  GIS,  commonly referred to as GRASS (Geographic Resources Analysis Support System),
       is a free Geographic Information System (GIS) software used for geospatial data management
       and   analysis,   image   processing,  graphics/maps  production,  spatial  modeling,  and
       visualization. GRASS GIS is currently used in academic and commercial settings around  the
       world,  as  well  as by many governmental agencies and environmental consulting companies.
       GRASS GIS is an official project of the Open Source Geospatial Foundation (OSGeo).

1. Startup of GRASS GIS

       After launching GRASS GIS, the startup screen will open:

   GRASS data are stored in a directory referred to as DATABASE
       (also called "GISDBASE").  This directory has to be created with a  file  manager  or  the
       mkdir command, before starting to work with GRASS.  Within this DATABASE, the projects are
       organized by project areas stored in subdirectories called LOCATIONs.

   A LOCATION is defined by its coordinate system, map projection and
       geographical boundaries. The subdirectories and files  defining  a  LOCATION  are  created
       automatically when GRASS is started the first time with a new LOCATION. It is important to
       understand that each projection stays in its own LOCATION.

       See the "Location Wizard"  to easily create a new LOCATION from scratch  from  a  geocoded
       file, by defining the parameters or by selecting the corresponding EPSG projection code.

   Each LOCATION can have many MAPSETs. Each MAPSET is a LOCATION's
       subdirectory. New MAPSET can be added at GRASS startup (see related button).

   The "Location Wizard" let's you easily create a new LOCATION. You
       will  be  guided through a series of dialogues to browse and select predefined projections
       (also via EPSG code) or to define individual projections. Find below some rules to  define
       the default raster resolution for a new LOCATION.

   Once you have selected an existing LOCATION/MAPSET or defined a new
       one,  you  can  enter  GRASS. The graphical user interface wxGUI will open and provide you
       with a menu system, map visualization tool, digitizer, and more.

2. Background: GRASS GIS Location structure

       A LOCATION is simply a set of directories which contains the  GRASS  data  of  a  project.
       Within  each  LOCATION,  a  mandatory  "PERMANENT" MAPSET exists which contains projection
       information and some more definitions. It can be used to store the base cartography in  it
       as "PERMANENT" is visible to all users accessing a LOCATION.

       Fig. 1: GRASS GIS location structure

   Creating and maintaining MAPSETs
       One motivation to maintain different MAPSETs is to store maps related to project issues or
       subregions. Another motivation is to support simultaneous access of several users  to  the
       map  layers  stored  within the same LOCATION, i.e. teams working on the same project. For
       teams a centralized GRASS DATABASE would be defined in a network file system  (e.g.  NFS).
       Besides  access  to his/her own MAPSET, each user can also read map layers in other users'
       MAPSETs, but s/he can modify or remove only the map layers in his/her own MAPSET.

       You can learn more about mapsets and how to seamlessly access maps found in another MAPSET
       of the same LOCATION in the g.mapsets documentation.

   The role of the PERMANENT LOCATION
       When  creating  a  new  LOCATION,  GRASS  automatically  creates  a  special MAPSET called
       PERMANENT where the core data for the project can be stored. Data in the PERMANENT  MAPSET
       can only be added, modified or removed by the owner of the PERMANENT MAPSET; however, they
       can be accessed, analyzed, and copied into their  own  MAPSET  by  the  other  users.  The
       PERMANENT  MAPSET  is useful for providing general spatial data (e.g. an elevation model),
       accessible but write-protected to all users who are working in the same  LOCATION  as  the
       database  owner.   To manipulate or add data to PERMANENT, the owner would start GRASS and
       choose the relevant LOCATION and the PERMANENT MAPSET.   This  mapset  also  contains  the
       DEFAULT_WIND  file,  which  holds  the  default  region boundary coordinate values for the
       location (which all users will inherit when they start using the database).  Additionally,
       in all mapsets a WIND file is kept, for storing the current boundary coordinate values and
       the currently selected raster resolution.  Users have the option of switching back to  the
       default region at any time.

3. Creating a GRASS Database with Sample Data

       To create the GRASS database:

               Find  a  place  on  your disk where you have write access and that has enough disk
              space to hold your spatial data.

               Create a subdirectory that will hold the general GRASS database (e.g. using a file
              manager or with mkdir /data/grassdata or mkdir /home/yourlogin/grassdata).

       Sample  data  such  as  the  "Spearfish"  or  the  "North Carolina" sample datasets may be
       downloaded  from   and   the   compressed   data
       package(s) extracted into this new database directory.

       Now  you  are ready to select a sample dataset in the GRASS GIS startup screen (see above)
       and start the session.

4. Creating A New Location with the Location Wizard

       The wxGUI graphical user interface provides a graphical "Location Wizard" which let's  you
       easily  create  a  new  LOCATION  for  own  data.  You  will be guided through a series of
       dialogues to browse and select predefined projections (also via EPSG code)  or  to  define
       individual  projections.  The rules to define the resolution as described above also apply

       Hint: You can create new location easily from a georeferenced data file.  In this case you
       are  asked  whether  the data itself should be imported into the new location. The default
       region is then set to match imported map and the GRASS GIS session is opened.

       After defining new location, wxGUI starts automatically.  If data were  already  imported,
       you  can  add  them into the Layer Manager now and display them. If your location is empty
       you can import your data from the menu: Go to "File" -> "Import raster/vector  data"  (see
       also the related Wiki page on Importing data).

Further Reading

       Please   have   a   look   at   the   GRASS   GIS   web  site  for  tutorials  and  books:

See also

        GRASS GIS 6 Reference Manual
       GRASS GIS 6 startup program manual page

       Last changed: $Date: 2013-03-28 12:36:16 -0700 (Thu, 28 Mar 2013) $

       GRASS GIS 6 Reference Manual Help Index

       © 2005-2012 GRASS Development Team